What are the recommended screening intervals and trimester‑specific management (oral iron, intravenous iron, and transfusion thresholds) for anemia in pregnant patients?

Trimester-Specific Management of Anemia in Pregnancy

Screening Protocol

All pregnant women should be screened for anemia at the first prenatal visit and again at 24-28 weeks gestation using hemoglobin or hematocrit testing. 1

• Confirm positive screening results with repeat testing before initiating treatment 1
• Anemia is defined as hemoglobin <11.0 g/dL in the first trimester and <10.5 g/dL in the second and third trimesters 2
• In non-acutely ill pregnant women, make a presumptive diagnosis of iron deficiency anemia and begin treatment immediately without waiting for additional testing 1

Universal Prophylaxis (All Trimesters)

Begin low-dose oral iron supplementation (30 mg/day of elemental iron) at the first prenatal visit for all pregnant women, regardless of anemia status. 3

• Continue this prophylactic dose throughout pregnancy and the postpartum period 3
• Take iron between meals to maximize absorption 3
• Encourage consumption of iron-rich foods and foods that enhance iron absorption 4

Treatment Algorithm by Severity

Mild to Moderate Anemia (Hemoglobin 9.0-10.4 g/dL)

Prescribe 60-120 mg/day of elemental iron orally as first-line therapy. 1

• Provide dietary counseling emphasizing iron-rich foods 1
• Reassess hemoglobin or hematocrit after 4 weeks of treatment 1
• Expected response: hemoglobin increase ≥1 g/dL or hematocrit increase ≥3% 1
• Once hemoglobin normalizes for gestational age, reduce dose to 30 mg/day for maintenance 1

Severe Anemia (Hemoglobin <9.0 g/dL or Hematocrit <27.0%)

Refer to a physician familiar with anemia management in pregnancy for further medical evaluation. 4

• Consider intravenous iron therapy as first-line option for hemoglobin <9.0 g/dL beyond 14 weeks gestation 5
• Intravenous iron is superior to oral iron for hematological response and should be strongly considered in the second and third trimesters 5, 6
• Ferric carboxymaltose is the preferred intravenous formulation due to rapid effectiveness and better tolerability 1
• Intravenous iron doses of 600-1200 mg are typically required 5

Management of Non-Response to Oral Iron

If anemia does not respond after 4 weeks of oral iron treatment despite compliance and absence of acute illness, perform additional testing including mean corpuscular volume, red cell distribution width, and serum ferritin. 1

• Switch to intravenous iron if oral therapy fails after 4 weeks with confirmed adherence 1
• In women of African, Mediterranean, or Southeast Asian ancestry, consider thalassemia minor or sickle cell trait as causes of iron-refractory anemia 1
• Confirm compliance before switching to intravenous therapy, as gastrointestinal side effects commonly lead to treatment discontinuation 1

Trimester-Specific Considerations

First Trimester

• Screen at first prenatal visit 1
• Begin universal prophylaxis with 30 mg/day elemental iron 3
• Treat confirmed anemia with 60-120 mg/day oral iron 1
• Limited experience with intravenous iron in first trimester; reserve for severe cases 5

Second Trimester

• Continue prophylaxis or treatment as indicated 3
• Intravenous iron is considered safe and should be used for severe anemia or oral iron failure 5
• If hemoglobin >15.0 g/dL or hematocrit >45.0%, evaluate for poor blood volume expansion and potential pregnancy complications 1

Third Trimester

• Rescreen at 24-28 weeks gestation 1
• Intravenous iron should be considered as first-line option for any newly diagnosed anemia to ensure adequate correction before delivery 5
• Profound anemia in third trimester requires prompt intervention with intravenous iron due to serious consequences for both woman and fetus 5

Special Populations

Vegetarian women may require nearly double the standard iron supplementation due to lower absorption of non-heme iron from plant sources. 3

Postpartum Management

Screen women at risk for anemia at 4-6 weeks postpartum using hemoglobin or hematocrit. 1

• Risk factors include anemia persisting through third trimester, excessive blood loss at delivery, and multiple birth 1
• Continue iron supplementation throughout the postpartum period to prevent recurrence 1

Critical Thresholds and Warnings

• Hemoglobin <9.0 g/dL or hematocrit <27.0% requires specialist referral 1
• Blood transfusion is not indicated in stable pregnant patients with hemoglobin around 9 g/dL without active bleeding or hemodynamic instability 1
• Do not delay iron therapy while waiting for confirmatory laboratory tests, as this can lead to worsening anemia and adverse pregnancy outcomes 1
• Gastrointestinal side effects are common with oral iron but generally self-limited 1